From mboxrd@z Thu Jan 1 00:00:00 1970 From: "christian pellegrin" Subject: Re: possible problem in s3c24xx-pcm.c in git-devel branch Date: Thu, 13 Nov 2008 16:40:03 +0100 Message-ID: References: <20081113151701.GG31592@sirena.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from rv-out-0708.google.com (rv-out-0708.google.com [209.85.198.251]) by alsa0.perex.cz (Postfix) with ESMTP id 5B7FE10380E for ; Thu, 13 Nov 2008 16:40:04 +0100 (CET) Received: by rv-out-0708.google.com with SMTP id f25so983689rvb.32 for ; Thu, 13 Nov 2008 07:40:03 -0800 (PST) In-Reply-To: <20081113151701.GG31592@sirena.org.uk> Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: Mark Brown Cc: David Anders , alsa-devel@alsa-project.org, Ben Dooks List-Id: alsa-devel@alsa-project.org On Thu, Nov 13, 2008 at 4:17 PM, Mark Brown wrote: > On Thu, Nov 13, 2008 at 03:57:08PM +0100, christian pellegrin wrote: > >> >> but this really could be "playing with DMA" since I'm not sure why >> there is a 1 (since min_period is 2 I would guess 2 is the right >> value). Anyway with this change play and capture work well. > > See the commit log - the underlying DMA code restricts the number of > buffers that can be queued up prior to the start of DMA. > >> AFAIK it's limited to 2 transfers, one loaded and one running. It could beneficial to have more of them (so the DMA doesn't stop if one interrupt is delayed for too much time). But I don't know if it's so critical. A period (4k) with cd quality sound takes 23 ms to be played. An embedded system not responding to irqs for all this time probably has worse issues. -- Christian Pellegrin, see http://www.evolware.org/chri/ "Real Programmers don't play tennis, or any other sport which requires you to change clothes. Mountain climbing is OK, and Real Programmers wear their climbing boots to work in case a mountain should suddenly spring up in the middle of the computer room."